1. Osmosis and Diffusion
Potato Lab

2. What is osmosis and diffusion?
Osmosis is the movement of water across a cell membrane from an area of higher concentration to an area of lower concentration.
Diffusion is the movement of molecules other than water across a membrane from an area of higher concentration to and area of lower concentration.

3. Can a potato be used to demonstrate osmosis and diffusion?
Potatoes are composed of cells.
Potato cells have cell membranes.
Potato cells have some water and some salt inside the cells.

5. Potato Lab Design the Experiment
What can we observe that would be evidence of osmosis and diffusion?
What can we measure to see if a change takes place?
What is the process that will cause a change?
What is the variable? What is the control?

6. Materials 2 Potato slices 2 cups 1 teaspoon of salt Water Balance
Marker to label cups

7. Hypothesis
Water Cup-Water will move from the cup into the potato because water outside the cell will be in higher concentration than water inside the cell. This is an example of hypotonic solution.
Salt Water Cup- Salt will move into the cell from the cup and water will move out of the cell into the cup because of a difference in concentration. This is a hypertonic solution.

8. Procedure Label one cup water. Label the other cup salt water.
Measure the mass of a potato slice. Record the mass on a cup and place the slice in the cup. Repeat so that each cup has one potato slice.

9. Procedure
Add the same amount of water to each cup so that the potato slices are covered with water.
Add 1 teaspoon of salt to the cup labeled salt water. Make sure that the salt dissolves.
Let both cups sit at least overnight.

10. Predictions What do expect to see on Monday?
What will each potato feel like on Monday?
What will each potato look like on Monday?
What will happen to the mass of each potato when you measure it on Wednesday?

11. Sample Data for Quiz Review
Condition
Initial Mass
Final Mass
Change in mass
Texture change
Potato in tap water
12 grams
14 grams
+2 grams
More rigid, firmer
Potato in salt water
11.5 grams
10 grams
-1.5 grams
Less rigid, softer
Does osmosis explain the changes? Why?